PLT-1598 Slash command works in RHS (#4367)

* PLT-1598 Slash command works in RHS

* fix UserProfile in the reply for Slash Command

* fix some problem about the system messages in RHS
* system message in RHS isn't displayed as comment for root message

* remove status indicator for system message in RHS

* system message in RHS is colored to grey

* system messages don't count as commented post

* fix bug about cleaning draft in RHS

* remove unnecessary function

* implement new model for executing command

api/command_loadtest_test.go

@@ -25,7 +25,7 @@ func TestLoadTestHelpCommands(t *testing.T) {
 
 	utils.Cfg.ServiceSettings.EnableTesting = true
 
-	rs := Client.Must(Client.Command(channel.Id, "/loadtest help", false)).Data.(*model.CommandResponse)
+	rs := Client.Must(Client.Command(channel.Id, "/loadtest help")).Data.(*model.CommandResponse)
 	if !strings.Contains(rs.Text, "Mattermost load testing commands to help") {
 		t.Fatal(rs.Text)
 	}
@@ -46,7 +46,7 @@ func TestLoadTestSetupCommands(t *testing.T) {
 
 	utils.Cfg.ServiceSettings.EnableTesting = true
 
-	rs := Client.Must(Client.Command(channel.Id, "/loadtest setup fuzz 1 1 1", false)).Data.(*model.CommandResponse)
+	rs := Client.Must(Client.Command(channel.Id, "/loadtest setup fuzz 1 1 1")).Data.(*model.CommandResponse)
 	if rs.Text != "Created enviroment" {
 		t.Fatal(rs.Text)
 	}
@@ -67,7 +67,7 @@ func TestLoadTestUsersCommands(t *testing.T) {
 
 	utils.Cfg.ServiceSettings.EnableTesting = true
 
-	rs := Client.Must(Client.Command(channel.Id, "/loadtest users fuzz 1 2", false)).Data.(*model.CommandResponse)
+	rs := Client.Must(Client.Command(channel.Id, "/loadtest users fuzz 1 2")).Data.(*model.CommandResponse)
 	if rs.Text != "Added users" {
 		t.Fatal(rs.Text)
 	}
@@ -88,7 +88,7 @@ func TestLoadTestChannelsCommands(t *testing.T) {
 
 	utils.Cfg.ServiceSettings.EnableTesting = true
 
-	rs := Client.Must(Client.Command(channel.Id, "/loadtest channels fuzz 1 2", false)).Data.(*model.CommandResponse)
+	rs := Client.Must(Client.Command(channel.Id, "/loadtest channels fuzz 1 2")).Data.(*model.CommandResponse)
 	if rs.Text != "Added channels" {
 		t.Fatal(rs.Text)
 	}
@@ -109,7 +109,7 @@ func TestLoadTestPostsCommands(t *testing.T) {
 
 	utils.Cfg.ServiceSettings.EnableTesting = true
 
-	rs := Client.Must(Client.Command(channel.Id, "/loadtest posts fuzz 2 3 2", false)).Data.(*model.CommandResponse)
+	rs := Client.Must(Client.Command(channel.Id, "/loadtest posts fuzz 2 3 2")).Data.(*model.CommandResponse)
 	if rs.Text != "Added posts" {
 		t.Fatal(rs.Text)
 	}